An aneurysm develops when the repeated shock of blood flowing through a vessel causes a weakened vessel wall to bulge. Untreated, an aneurysm can eventually rupture causing bleeding and leading to hypovolemic shock and eventually death. Fortunately, stent grafts can be used to bypass the damaged portion of the blood vessel. The stent graft is placed on an introducer and the combined assembly is introduced into the patient percutaneously. The assembly is advanced through a patient's vasculature to the treatment site, and then the stent graft is deployed at the site of the aneurysm.
The size of a patient's vasculature and the size of the assembly can limit options for treatment. For example, potentially effective stent graft and introducer systems may be too large to fit into and traverse smaller vasculature safely. Thus there is an advantage to reducing the compressed size of the stent graft and the introducer. One method of reducing stent graft size is to reduce the features on the stent graft. This has the additional advantage of eliminating unnecessary manufacturing steps.
In addition, accurate and effective placement of the stent graft in vasculature can be tricky. For example, a stent graft may need to be placed such that its ends seal against the walls of the blood vessel above and below the aneurysm. When placed correctly, blood pressure is redirected against the walls of the stent graft instead of the weakened vessel wall. This decreases the likelihood that the aneurysm will enlarge or rupture.
Where the aneurysmal area includes branch vessels, it may be desirable to preserve the natural path of blood flow from the affected vessel to its side branches to ensure continued perfusion of peripheral body systems. One method of preserving blood flow to peripheral vessels utilizes connecting stents deployed through fenestrations in the stent graft's side wall. This method fluidly links the stent graft lumen to the side branch lumen via the connecting stent lumen. For example, a stent graft placed in the abdominal aorta may block the renal arteries and impair the function of the kidneys unless connecting stents can be deployed in the stent graft wall fenestrations that abut the ostia of the renal arteries.
A problem arises when the unique proportions of a patient's vessel do not match the proportions of a manufactured stent graft. This can occur when the aneurysm is located in a vessel such that the ostium of a branch vessel will not align with the manufactured stent graft fenestration when deployed.
For example, a stent graft may have a fenestration which is centered at 20 mm from its end. However, a target vessel may have a side branch centered at 25 mm from the end when the stent graft is deployed. Thus, the deployed stent graft will partially occlude the side branch. The difficulty of cannulating the side branch and deploying a connecting stent is increased, and even when the connecting stent is successfully deployed, the connecting stent may be pinched, restricting blood flow to the side branch.
This problem is further compounded as the number of fenestrations and target side branches increase. For example, two fenestrations on a stent graft may be 15 mm from each other, but the side branches of the vessel are 20 mm from each other. Deploying the stent graft will result in partial occlusion of both side branches. In the alternative, one side branch can be fully aligned, but at the cost of further occlusion of the remaining side branch.
Prior attempts at addressing this problem use various methods of making the fenestrations adjustable. For example, a reinforced dome around the fenestration allows the connecting stent to tilt and adjust its angle. Huser (US Patent App 20120046728). The use of corrugated graft material near the fenestration provides some flexibility to the fenestration Hartley (U.S. Pat. No. 7,645,298).
There is a need in the art for an improved adjustable fenestration that can safely and effectively link a stent graft lumen to a side branch lumen despite imperfect matching of the fenestration and the side branch.